---
id: CVE-2026-109363
title: >-
  ZcashFoundation Zebra 6.4.0 before 6.4.2 parses version 6 transactions
  carrying a pre-NU6.3 consensus branch ID, but the size computation during
  UnminedTx construction treats re-serialization of the Orchard bundle as
  infallible, so the r…
summary: >-
  ZcashFoundation Zebra 6.4.0 before 6.4.2 parses version 6 transactions
  carrying a pre-NU6.3 consensus branch ID, but the size computation during
  UnminedTx construction treats re-serialization of the Orchard bundle as
  infallible, so the r…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-617
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T17:17:33.953'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109363'
references:
  - url: >-
      https://github.com/ZcashFoundation/zebra/commit/008abac5c99e872f283450d596d95e37851df49a
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-h5rr-8pqv-grp9
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/zebra-6.4.0-before-6.4.2-denial-of-service-via-malformed-v6-transaction
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-12T18:00:08.214Z'
---

## Overview

ZcashFoundation Zebra 6.4.0 before 6.4.2 parses version 6 transactions carrying a pre-NU6.3 consensus branch ID, but the size computation during UnminedTx construction treats re-serialization of the Orchard bundle as infallible, so the resulting error trips an expect that aborts zebrad. Unauthenticated peers can send a single pre-handshake tx message to crash the node, and can repeat this after each restart.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.